Such a process chamber is presented and described in DE OS 4416959. This process chamber employs a fan wheel which draws in gas, more particularly air, from the environment and supplies it into a channel, said channel extending between the walls of the process chamber and being directed onto the printed circuit boards which are to be treated. The gas is supplied to the fan wheel via the periphery thereof and is carried away from the surface thereof, the gas also partially entering the open interior space of the fan wheel and, owing to the rotation thereof and the blades contained in the fan wheel, being transported away therefrom because of the centrifugal force imparted to the gas. It has been shown that, with such a process chamber, it is possible to produce gas streams of only limited gas pressure. In order to produce the gas velocity necessary for the treatment of the printed circuit boards, the fan wheel must be operated at high rotational speed, something which is undesired in view of the required drive and wear of the bearings; of the fan wheel. There is also the fact that the melting of the solder applied to the printed circuit boards calls for a high temperature, e.g. up to 400° C., of the gas, this correspondingly increasing the tendency to wear, especially of the bearings of the fan wheel.